Inbred sweet corn line R660K

ABSTRACT

An inbred sweet corn line, designated R660K, the plants and seeds of inbred sweet corn line R660K, methods for producing a maize plant produced by crossing the inbred sweet corn line R660K with itself or with another maize plant, and hybrid maize seeds and plants produced by crossing the inbred sweet corn line R660K with another maize line or plant.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/815,200 filed Jun. 20, 2006. The above application is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

This invention is in the field of maize breeding, specifically relatingto an inbred sweet corn line designated R660K.

BACKGROUND OF THE INVENTION

The goal of plant breeding is to combine in a single variety or hybridvarious desirable traits. For vegetable crops, such as sweet corn, thesetraits may include resistance to diseases and insects, tolerance to heatand drought, reducing the time to crop maturity, greater yield, betteragronomic quality, processing traits, such as high processing plantrecovery, tender kernels, pleasing taste, uniform kernel size and color,attractive husk package and husked ears, ability to ship long distances,ease of mechanical or manual harvest, tipfill, row straight. Withmechanical harvesting of many crops, uniformity of plant characteristicssuch as germination and stand establishment, growth rate, maturity, andplant and ear height, is important.

Sweet corn is a particular type of maize (Zea mays L., often referred toas corn in the United States). Sweet corn is harvested at an earliermaturity than field corn (before it is dry), for a different purpose(usually fresh produce, canning or freezing, for human consumption) andhas been bred therefore to be qualitatively and quantitatively differentfrom field corn in a number of respects.

Maize is bred through techniques that take advantage of the plant'smethod of pollination. A plant is self-pollinated if pollen from oneflower is transferred to the same or another flower of the same plant. Aplant is cross-pollinated if the pollen comes from a flower on adifferent plant. Plants that have been self-pollinated and selected fortype for many generations become homozygous at almost all gene loci andproduce a uniform population of true breeding progeny. A cross betweentwo different homozygous lines produces a uniform population of hybridplants that may be heterozygous for many gene loci. A cross of twoplants each heterozygous at a number of gene loci will produce apopulation of hybrid plants that differ genetically and will not beuniform.

Maize can be bred by both self-pollination and cross-pollinationtechniques. Maize has separate male and female flowers on the sameplant, located on the tassel and the ear, respectively. Naturalpollination occurs in maize when wind blows pollen from the tassels tothe silks that protrude from the tops of the ears.

A reliable method of controlling male fertility in plants offers theopportunity for improved plant breeding. This is especially true fordevelopment of maize hybrids, which relies upon some sort of malesterility system. There are several options for controlling malefertility available to breeders, such as: manual or mechanicalemasculation (or detasseling), cytoplasmic male sterility, genetic malesterility, gametocides and the like. Hybrid maize seed is typicallyproduced by a male sterility system incorporating manual or mechanicaldetasseling. Alternate strips of two maize inbreds are planted in afield, and the pollen-bearing tassels are removed from one of theinbreds (female). Providing that there is sufficient isolation fromsources of foreign maize pollen, the ears of the detasseled inbred willbe fertilized only from the other inbred (male), and the resulting seedis therefore hybrid and will form hybrid plants.

The laborious, and occasionally unreliable, detasseling process can beavoided by using cytoplasmic male-sterile (CMS) inbreds. Plants of a CMSinbred are male sterile as a result of factors resulting from thecytoplasmic, as opposed to the nuclear, genome. Thus, thischaracteristic is inherited exclusively through the female parent inmaize plants, since only the female provides cytoplasm to the fertilizedseed. CMS plants are fertilized with pollen from another inbred that isnot male-sterile. Pollen from the second inbred may or may notcontribute genes that make the hybrid plants male-fertile. Seed fromdetasseled fertile maize and CMS produced seed of the same hybrid can beblended to insure that adequate pollen loads are available forfertilization when the hybrid plants are grown.

There are several methods of conferring genetic male sterilityavailable, such as multiple mutant genes at separate locations withinthe genome that confer male sterility, as disclosed in U.S. Pat. Nos.4,654,465 and 4,727,219 to Brar et al. and chromosomal translocations asdescribed by Patterson in U.S. Pat. Nos. 3,861,709 and 3,710,511. Theseand all patents referred to are incorporated by reference.

There are many other methods of conferring genetic male sterility in theart, each with its own benefits and drawbacks. These methods use avariety of approaches such as delivering into the plant a gene encodinga cytotoxic substance associated with a male tissue specific promoter oran antisense system in which a gene critical to fertility is identifiedand an antisense to that gene is inserted in the plant (see:Fabinjanski, et al. EPO 89/3010153.8 publication no. 329,308 and PCTapplication PCT/CA90/00037 published as WO 90/08828).

Another system useful in controlling male sterility makes use ofgametocides. Gametocides are not a genetic system, but rather a topicalapplication of chemicals. These chemicals affect cells that are criticalto male fertility. The application of these chemicals affects fertilityin the plants only for the growing season in which the gametocide isapplied (see Carlson, Glenn R., U.S. Pat. No. 4,936,904). Application ofthe gametocide, timing of the application and genotype specificity oftenlimit the usefulness of the approach.

The use of male sterile inbreds is but one factor in the production ofmaize hybrids. The development of maize hybrids requires, in general,the development of homozygous inbred lines, the crossing of these lines,and the evaluation of the crosses. Pedigree breeding and recurrentselection breeding methods are used to develop inbred lines frombreeding populations. Breeding programs combine the genetic backgroundsfrom two or more inbred lines or various other germplasm sources intobreeding pools from which new inbred lines are developed by selfing andselection of desired phenotypes. The new inbreds are crossed with otherinbred lines and the hybrids from these crosses are evaluated todetermine which of those have commercial potential. Plant breeding andhybrid development are expensive and time consuming processes.

Pedigree breeding starts with the crossing of two genotypes, each ofwhich may have one or more desirable characteristics that is lacking inthe other or which complements the other. If the two original parents donot provide all the desired characteristics, other sources can beincluded in the breeding population. In the pedigree method, superiorplants are selfed and selected in successive generations. In thesucceeding generations the heterozygous condition gives way tohomogeneous lines as a result of self-pollination and selection.Typically in the pedigree method of breeding five or more generations ofselfing and selection is practiced: F1 to F2; F3 to F4; F4 to F5, etc.

Recurrent selection breeding can be used to improve populations ofeither self or cross-pollinating crops. Recurrent selection can be usedto transfer a specific desirable trait from one inbred or source to aninbred that lacks the trait. This can be accomplished, for example, byfirst a superior inbred (recurrent parent) to a donor inbred(non-recurrent parent), that carries the appropriate gene(s) for thetrait in question. The progeny of this cross is then mated back to thesuperior recurrent parent followed by selection in the resultant progenyfor the desired trait to be transferred from the non-recurrent parent.After five or more backcross generations with selection for the desiredtrait, the progeny will be homozygous for loci controlling thecharacteristic being transferred, but will be like the superior parentfor essentially all other genes. The last backcross generation is thenselfed to give pure breeding progeny for the gene(s) being transferred.A hybrid developed from inbreds containing the transferred gene(s) isessentially the same as a hybrid developed from the same inbreds withoutthe transferred genes, except for the difference made by the transferredgene. As the varieties developed using recurrent selection breedingcontain almost all of the characteristics of the recurrent parent,selecting a superior recurrent parent is desirable.

A single cross maize hybrid results from the cross of two inbred lines,each of which has a genotype that complements the genotype of the other.The hybrid progeny of the first generation is designated F1. In thedevelopment of commercial hybrids only the F1 hybrid plants are sought.Preferred F1 hybrids are more vigorous than their inbred parents. Thishybrid vigor, or heterosis, can be manifested in many polygenic traits,including increased vegetative growth and increased yield.

The development of a maize hybrid involves three steps: (1) theselection of plants from various germplasm pools for initial breedingcrosses; (2) the selfing of the selected plants from the breedingcrosses for several generations to produce a series of inbred lines,which, although different from each other, breed true and are highlyuniform; and (3) crossing the selected inbred lines with differentinbred lines to produce the hybrid progeny (F1). During the inbreedingprocess in maize, the vigor of the lines decreases. Vigor is restoredwhen two different inbred lines are crossed to produce the hybridprogeny (F1). An important consequence of the homozygosity andhomogeneity of the inbred lines is that the hybrid between a definedpair of inbreds will always have the same genotype. Once the inbredsthat give a superior hybrid have been identified, the hybrid seed can bereproduced indefinitely as long as the homogeneity of the inbred parentsis maintained.

A single cross hybrid is produced when two inbred lines are crossed toproduce the F1 progeny. A double cross hybrid is produced from fourinbred lines crossed in pairs (A×B and C×D) and then the two F1 hybridsare crossed again (A×B)×(C×D). Much of the hybrid vigor exhibited by F1hybrids is lost in the next generation (F2). Consequently, seed fromhybrids is not used for planting stock.

Hybrid seed production requires elimination or inactivation of pollenproduced by the female parent. Incomplete removal or inactivation of thepollen provides the potential for self pollination. This inadvertentlyself pollinated seed may be unintentionally harvested and packaged withhybrid seed. Once the seed is planted, it is possible to identify andselect these self pollinated plants. These self pollinated plants willbe genetically equivalent to the female inbred line used to produce thehybrid. Typically these self pollinated plants can be identified andselected due to their decreased vigor. Female selfs are identified bytheir less vigorous appearance for vegetative and/or reproductivecharacteristics, including shorter plant height, small ear size, ear andkernel shape, cob color, or other characteristics.

Identification of these self pollinated lines can also be accomplishedthrough molecular marker analyses. See, “The Identification of FemaleSelfs in Hybrid Maize: A Comparison Using Electrophoresis andMorphology”, Smith, J. S. C. and Wych, R. D., Seed Science andTechnology 14, pp. 1-8 (1995). Through these technologies, thehomozygosity of the self pollinated line can be verified by analyzingallelic composition at various loci along the genome. Those methodsallow for rapid identification of the invention disclosed herein. Seealso, “Identification of Atypical Plants in Hybrid Maize Seed byPostcontrol and Electrophoresis” Sarca, V. et al., Probleme de GeneticaTeoretica si Aplicata Vol. 20 (1) p. 29-42.

As is readily apparent to one skilled in the art, the foregoing are onlytwo of the various ways by which the inbred can be obtained by thoselooking to use the germplasm. Other means are available, and the aboveexamples are illustrative only.

Sweet corn is an important and valuable vegetable crop. Thus, acontinuing goal of plant breeders is to develop high-yielding hybridsthat are agronomically sound based on stable inbred lines. The reasonsfor this goal are obvious: to maximize the amount of marketable sweetcorn produced with the inputs used and minimize susceptibility of thecrop to pests and environmental stresses. To accomplish this goal, thebreeder must select and develop superior inbred parental lines forproducing hybrids. This requires identification and selection ofgenetically unique individuals that occur in a segregating population.The segregating population is the result of a combination of crossoverevents plus the independent assortment of specific combinations ofalleles at many gene loci that results in specific genotypes. Theprobability of selecting any one individual with a specific genotypefrom a breeding cross is very low due to the large number of segregatinggenes and the unlimited recombinations of these genes, some of which maybe closely linked. However, the genetic variation among individualprogeny of a breeding cross allows for the identification of rare andvaluable new genotypes. These new genotypes are neither predictable norincremental in value, but rather the result of manifested geneticvariation combined with selection methods, environments and the actionsof the breeder.

Thus, even if the entire genotypes of the parents of the breeding crosswere characterized and a desired genotype known, only a few, if any,individuals having the desired genotype may be found in a largesegregating F2 population. Typically, however, neither the genotypes ofthe breeding cross parents nor the desired genotype to be selected isknown in any detail. In addition, it is not known how the desiredgenotype would react with the environment. This genotype by environmentinteraction is an important, yet unpredictable, factor in plantbreeding. A breeder of ordinary skill in the art cannot predict thegenotype, how that genotype will interact with various climaticconditions or the resulting phenotypes of the developing lines, exceptperhaps in a very broad and general fashion. A breeder of ordinary skillin the art would also be unable to recreate the same line twice from thevery same original parents as the breeder is unable to direct how thegenomes combine or how they will interact with the environmentalconditions. This unpredictability results in the expenditure of largeamounts of research resources in the development of a superior new maizeinbred line, such as a superior new sweet corn inbred line.

SUMMARY OF THE INVENTION

According to the invention, there is provided a novel inbred sweet cornline, designated R660K. This invention thus relates to the seeds ofinbred sweet corn line R660K, to the plants of inbred sweet corn lineR660K and parts thereof, for example pollen, ovule, or ear, and tomethods for producing a maize plant, preferably a sweet corn plant, bycrossing the inbred line R660K with itself or another maize line,preferably a sweet corn line. This invention further relates to hybridmaize seeds, preferably hybrid sweet corn seeds, and plants produced bycrossing the inbred line R660K with another maize line, preferably asweet corn line.

The invention is also directed to inbred sweet corn line R660K intowhich one or more specific, single gene traits, for example transgenes,have been introgressed from another maize line, such as a field cornline or a sweet corn line, and which has essentially all of themorphological and physiological characteristics of inbred sweet cornline of R660K, in addition to the one or more specific, single genetraits introgressed into the inbred. The invention also relates to seedsof an inbred sweet corn line R660K into which one or more specific,single gene traits have been introgressed and to plants of an inbredsweet corn line R660K into which one or more specific, single genetraits have been introgressed. The invention further relates to methodsfor producing a maize plant, preferably a sweet corn plant, by crossingplants of an inbred sweet corn line R660K into which one or morespecific, single gene traits have been introgressed with themselves orwith another maize line, such as a field corn line or a sweet corn line.The invention also further relates to hybrid maize seeds, preferablysweet corn seeds, and plants produced by crossing plants of an inbredsweet corn line R660K into which one or more specific, single genetraits have been introgressed with another maize line, such as a fieldcorn line or a sweet corn line. The invention is also directed to amethod of producing inbreds comprising planting a collection of hybridseed, growing plants from the collection, identifying inbreds among thehybrid plants, selecting the inbred plants and controlling theirpollination to preserve their homozygosity.

The invention is also directed to a method of producing a sweet corn earcomprising growing a plant according to the instant invention to producean ear, and harvesting said ear. In one embodiment, the method furthercomprises isolating a kernel from said ear. In one embodiment, themethod further comprises processing said kernel to obtain a sweet cornproduct. In one embodiment, a sweet corn product according the instantinvention is a canned or a frozen product, or a fresh produce.

The invention is also directed to a method of producing a sweet cornproduct comprising obtaining an ear of a plant according to the instantinvention, isolating a kernel from said ear, and processing said kernelto obtain a sweet corn product. In one embodiment, a sweet corn productaccording the instant invention is a canned or a frozen product, or afresh produce.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention, there is provided a novel inbred sweet cornline, designated R660K. Inbred sweet corn line R660K was derived bymodified backcrossing and selfing primarily from the Syngentaproprietary inbred R660. The inbred line R660K has several desirablecharacters retained from R660 including high resistant to most races ofExserohilum turcicum, desirable ear appearance, good plant structure andresistance to lodging. It differs from R660 in that it carries thePuccinia sorghi (common rust) resistance gene Rp1-I, has resistance toMDMV (Maize Dwarf Mosaic Virus), has better husk leaf extension andshorter shank. The rust resistance gene RpI-I was first described inHagan, W. L. and A. L. Hooker (1965) Phytopathology 55:193-197. The rustresistance gene RpI-I was obtained from the publicly available fieldcorn line R168 [10].558, which is a BC10 introgression of the Rp1-I geneinto the field corn line R168. Inbred sweet corn line R660 is aproprietary Syngenta inbred sweet corn line, and is a parent of thecommercial hybrid Primetime. Some of the characteristics of inbred sweetcorn line R660K are illustrated in Table 1.

Inbred maize lines, such as sweet corn inbred lines, are typicallydeveloped for use in the production of hybrid maize lines, for examplehybrid sweet corn lines. Inbred maize lines need to be highlyhomogeneous, homozygous and reproducible to be useful as parents ofcommercial hybrids. There are many analytical methods available todetermine the homozygotic and phenotypic stability of these inbredlines. The oldest and most traditional method of analysis is theobservation of phenotypic traits. The data is usually collected in fieldexperiments over the life of the maize plants to be examined. Phenotypiccharacteristics often observed are for traits associated with plantmorphology, ear and kernel morphology, insect and disease resistance,maturity, and yield.

In addition to phenotypic observations, the genotype of a plant can alsobe examined. There are many laboratory-based techniques available forthe analysis, comparison and characterization of plant genotype; amongthese are Isozyme Electrophoresis, Restriction Fragment LengthPolymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs (RAPDs),Arbitrarily Primed Polymerase Chain Reaction (AP-PCR), DNA AmplificationFingerprinting (DAF), Sequence Characterized Amplified Regions (SCARs),Amplified Fragment Length Polymorphisms (AFLPs), Simple Sequence Repeats(SSRs) which are also referred to as Microsatellites, and SingleNucleotide Polymorphisms (SNPs).

Some of the most widely used of these laboratory techniques are IsozymeElectrophoresis and RFLPs as discussed in Lee, M., “Inbred Lines ofMaize and Their Molecular Markers,” The Maize Handbook,(Springer-Verlag, New York, Inc. 1994, at 423-432). IsozymeElectrophoresis is a useful tool in determining genetic composition,although it has relatively low number of available markers and the lownumber of allelic variants among maize inbreds. RFLPs have the advantageof revealing an exceptionally high degree of allelic variation in maizeand the number of available markers is almost limitless. Maize RFLPlinkage maps have been rapidly constructed and widely implemented ingenetic studies. One such study is described in Boppenmaier, et al.,“Comparisons among strains of inbreds for RFLPs”, Maize GeneticsCooperative Newsletter, 65:1991, pg. 90. This study used 101 RFLPmarkers to analyze the patterns of two to three different deposits eachof five different inbred lines. The inbred lines had been selfed fromnine to 12 times before being adopted into two to three differentbreeding programs. It was results from these two to three differentbreeding programs that supplied the different deposits for analysis.These five lines were maintained in the separate breeding programs byselfing or sibbing and rogueing off-type plants for an additional one toeight generations. After the RFLP analysis was completed, it wasdetermined the five lines showed 0-2% residual heterozygosity. Althoughthis was a relatively small study, it can be seen using RFLPs that thelines had been highly homozygous prior to the separate strainmaintenance.

The breeding method used was pedigree ear to row. Inbred sweet corn lineR660K has shown uniformity and stability within the limits ofenvironmental influence for all the traits as described in the Table 1that follows. The inbred has been self-pollinated and ear-rowed asufficient number of generations with careful attention paid touniformity of plant type to ensure the homozygosity and phenotypicstability necessary to use in commercial production. The line has beenincreased both by hand and in isolated fields with continued observationfor uniformity. No variant traits have been observed or are expected ininbred sweet corn line R660K. Inbred sweet corn line R660K, beingsubstantially homozygous, can be reproduced by planting seeds of theline, growing the resulting maize plants under self-pollinating orsib-pollinating conditions with adequate isolation, and harvesting theresulting seed, using techniques familiar to the agricultural arts.

The production of maize hybrids, such as sweet corn hybrids, typicallycomprises planting in pollinating proximity seeds of, for example,inbred sweet corn line R660K and of a different inbred parent maizeline, cultivating the seeds of inbred sweet corn line R660K and of saiddifferent inbred parent maize plant into plants that bear flowers,emasculating the male flowers of inbred sweet corn line R660K or themale flowers of said different inbred parent maize plant to produce anemasculated plant, allowing cross-pollination to occur between inbredsweet corn line R660K and said different inbred parent maize plant andharvesting seeds produced on said emasculated plant. The harvested seedare grown to produce hybrid maize plants. In one embodiment, inbredsweet corn line R660K is crossed with another inbred sweet corn line toproduce hybrid sweet corn seeds. In one embodiment, inbred sweet cornline R660K is crossed with an inbred sweet corn line of the R398-type(see e.g. U.S. Pat. No. 6,034,306, incorporated herein by reference inits entirety) to produce hybrid sweet corn seeds. In several differentembodiments, resulting sweet corn hybrid lines are described in Tables3-4.

TABLES 1 AND 2: Comparison between Inbred Sweet Corn Line R660K withlines R660 and Ia5125

TABLE 1 660K 660 vs. 660 660K std LSD Sig mean std dev mean dev .05 Y/NPlant data Plant height (cm) 150.8 7.475 157.5 6.9 4.5 y Ear height (cm)59.6 6.3 53.9 4.9 3.6 y Internode length (cm) 10.5 0.5 10.1 0.6 0.4 yNumber of tillers 0.7 0.7 0.85 0.7 0.4 n Ears per stalk 1.000 0.0001.150 0.366 0.2 y Leaf data Width of ear node 8.6 0.6 8.95 0.5 0.4 yleaf (cm) Length of ear node 69.8 2.7 68.0 4.3 2.3 n leaf (cm) Number ofleaves 4.9 0.4 6.2 0.7 0.4 y above Leaf angle (degrees 77.0 3.8 63.3 2.92.1 y from top of stalk) Tassel data Number of primary 11.4 2.1 14.4 2.31.4 y lateral branches Branch angle (degrees 89.0 2.6 74.8 7.0 3.3 yfrom central spike) Tassel length (cm) 32.5 2.5 31.1 2.0 1.4 y Ear dataEar Length (cm) 12.7 1.4 12.5 1.3 0.8 n Ear diameter (cm) 4.2 0.7 3.60.3 0.3 y Row number 15.2 1.3 14.2 1.3 0.8 y Kernel Length (mm) 8.2 1.75.9 0.9 0.9 y Kernel width (mm) 5.5 1.1 5.4 1.0 0.7 n Kernel thickness(mm) 3.3 1.1 3.2 0.6 0.6 n Percentage of round 23% 18.0 10% 8.9 9.1 ykernels Weight of 100 10.2 1.1 8.8 0.7 0.6 y kernels(grams) Cob diameter(cm) 1.49 0.14 1.25 0.12 0.08 y 660K 660 Ia5125 Descriptive ratings Leafsheath pubescence 7 3 5.8 Marginal waves 3 3 4.8 Longitudinal creases 67 4.4 Kernel rows 2 2 2 Row alignment 1 1 1 Aleurone color pattern 1 1 1Endosperm type sh2 sh2 su Endosperm yellow yellow yellow colorAnthocyanin of brace 0 0 1 roots Color ratings* Anther 5Y   5Y 7.5GY 8/88/8 4/4 Glume 2.5GY   7.5GY 2.5Y  5/4 7/4 8/6 Leaf 5GY   5GY 7.5GY 4/44/6 5/8 silk 2.5GY   2.5GY 2.5GY 8/8 8/6 8/6 Husk 5GY   5GY 7.5GY 7/87/8 4/4 *Munsell color guide ratings

TABLE 2 660K vs. Ia5125 Ia5125 std LSD Sig mean dev .05 Y/N Plant dataPlant height (cm) 144.8 7.9 5.1 y Ear height (cm) 66.2 5.8 4.0 yInternode length (cm) 12.5 0.9 0.5 y Number of tillers 1.1 0.8 0.5 nEars per stalk 1.000 0.000 na n Leaf data Width of ear node leaf (cm)7.3 0.9 0.5 y Length of ear node leaf (cm) 79.3 7.1 3.6 y Number ofleaves above 4.7 0.5 0.3 n Leaf angle (degrees from top 49.0 3.1 2.3 yof stalk) Tassel data Number of primary lateral branches 14.7 3.6 2.0 yBranch angle (degrees from 44.3 3.7 2.1 y central spike) Tassel length(cm) 26.4 2.6 1.7 y Ear data Ear Length (cm) 11.2 1.6 1.0 y Ear diameter(cm) 4.4 0.4 0.4 n Row number 18.9 2.6 1.4 y Kernel Length (mm) 11.1 0.90.9 y Kernel width (mm) 7.8 0.9 0.6 y Kernel thickness (mm) 3.1 0.3 0.5n Percentage of round kernels 36.5 18.7 12.1 y Weight of 100 kernels(grams) 22.3 2.1 1.1 y Cob diameter (cm) 1.8 0.3 0.14 y In interpretingthe foregoing color designations, reference may be had to be made to theMunsell Glossy Book of Color, a standard color reference. Colorcodes: 1. light green, 2. medium green, 3. dark green, 4. very darkgreen, 5. green-yellow, 6. pale yellow, 7. yellow, 8. yellow-orange, 9.salmon, 10. pink-orange, 11. pink, 12. light red, 13. cherry red, 14.red, 15. red and white, 16. pale purple, 17. purple, 18. colorless, 19.white, 20. white capped, 21. buff, 22. tan, 23. brown, 24. bronze, 25.variegated, 26. other. Std Dev = Standard Deviation

Tables 1 and 2 show that Inbred sweet corn line R660K differssignificantly from lines R660 and Ia5125 for several traits.

Comparison Between Hybrids

Summary:

Garrison Prime Plus Signifcantly mean mean lsd 0.05 Different PlantHeight (ft) 6.4 6.4 0.5 no ear height (in) 24.6 25.0 3.3 no Shank(cm)7.8 7.2 1.5 no Length ave. (in) 7.6 7.5 0.3 no Diameter (in) 1.9 1.8 0.1yes Row number 17.9 15.4 1.5 yes husk length (cm) 4.7 2.7 1.1 yes TipFill (cm) 0.3 0.1 0.3 noData by Trial

TABLE 3 Garrison Plant Ear Ear Ear Row Husk Tip Height Height ShankLength Diameter number length fill Trial ID Year (ft) (in) (cm) ave.(in) (in) ave. (cm) (cm) T05NEP 2005 6.1 28 7 7.9 2.05 20.4 3.5 0 T05NMP2005 7 29 12 8 2 19.3 3 0 T05SBGL 2005 6 22 6 7.8 1.9 16.4 4 0 T05SGAL2005 6.8 26 8 7 1.75 18 4 0 T05WLD 2005 8.5 36 9 7.7 1.85 19.2 3 2T05NJS 2005 5 24 9 7.8 1.95 16.4 6 T05COLP 2005 8 34 12 7.7 2 16.6 3.5 006BR1-1325 2006 5 22 3 8 2 16 5 0 06B51-1207 2006 6.5 24 7 7.2 1.75 806SG1-0116 2006 6.5 25 4 7.7 1.95 5 2.5 06SG1-0115 2006 6 20 10 7.7 1.855 06SG1-0155 2006 6 20 10 7.7 1.85 18.4 5 0 06SG2-0317 2006 6 6.8 1.50.1 06SG2-0361 2006 7 28 7 7.5 1.7 7 0.5 06SG2-0470 2006 7 16 11 7 1.9 80 06B53-3207 2006 6.5 28 5 7.6 1.9 5 0.5 06GA3-0904 2006 6 24 8 7.5 1.97 06GA3-0815 2006 5 18 7 7.4 1.8 5 06GA3-0859 2006 6 20 8 7.8 1.9 560BR5-5312 2006 7.5 26 11 7.5 1.9 7 0 06B55-5211 2006 7 28 6 7.7 1.9 5 006FB2-0209 2006 6 7.2 4 0.5 06FG1-0165 2006 6 6.8 7 0 06FG2-0465 2006 67.3 3 0 06NMP-6217 2006 6.5 23 7 8.4 1.99 3 0 06FIF-1077 2006 6 20 5 7.21.7 3 0 06WST-0611 2006 7 8.25 1.5 0 Average: 6.4 24.6 7.8 7.6 1.9 17.94.7 0.3 st dev 0.8 4.9 2.5 0.4 0.1 1.6 1.8 0.7

TABLE 4 Prime plus Plant Ear Ear Ear Row Husk Tip Height Height ShankLength Diameter number length fill (ft) (in) (cm) ave. (in) (in) ave.(cm) (cm) T05NEP 2005 6.5 30 6 8 1.85 16 1 0 T05NMP 2005 7 29 10 8.21.85 16.7 0.5 0 T05SBGL 2005 6 22 7 7.7 1.7 15.5 1.5 0 T05SGAL 2005 7.530 4 7.7 1.7 16 1 0 T05WLD 2005 9 35 6 7.8 1.7 15.2 2 0.2 T05NJS 20055.5 25 15 7.8 1.75 14.8 2 0 T05COLP 2005 8 32 10 8.8 2 16.3 1 006BR1-1323 2006 5 24 5 7 2 12 4 0 06B51-1206 2006 6.5 24 10 7.7 1.6 506SG1-0111 2006 4 15 5 7.4 2 3 06SG1-0154 2006 6 20 5 7.4 1.65 16 1 006SG1-0112 2006 6 5 6.7 1.85 7 0.5 06SG2-0313 2006 7 7 1.5 0.106SG2-0360 2006 7 28 5 7.2 1.8 3 0 06SG2-0450 2006 6.5 16 5 7 1.8 5 006BR3-3339 2006 5.5 32 7 7.5 1.85 2 06GA3-0858 2006 6.5 22 7 7.5 1.75 406GA3-0811 2006 6 18 7 7.7 1.7 2.5 06GA3-0897 2006 6 22 7 7.5 1.8 460BR5-5310 2006 7.5 26 11 7.5 1.73 5 0 06B55-5210 2006 6.5 28 7 7.7 1.852 0 06FB2-0208 2006 6 6.8 3 0.1 06FG1-0164 2006 6.5 7 7 0 06FG2-04642006 6.5 7.1 2 0.2 06NMP-6174 2006 0 06FIF-1074 2006 6.5 22 7 8.1 1.8 30 06WST-0609 2006 6.5 8.25 0 0.1 Average: 6.4 25.0 7.2 7.5 1.8 15.4 2.70.1 st dev 1.0 5.5 2.7 0.5 0.1 1.4 1.9 0.1

The invention also encompasses plants of inbred sweet corn line R660Kand parts thereof further comprising one or more specific, single genetraits, which have been introgressed into inbred sweet corn line R660Kfrom another maize line. The single gene traits is transferred intoinbred sweet corn line R660K from any type of maize line, such as forexample a field corn line, a sweet corn line, a popcorn line, a whitecorn line or a silage corn line. Preferably, one or more new traits aretransferred to inbred sweet corn line R660K, or, alternatively, one ormore traits of inbred sweet corn line R660K are altered or substituted.The transfer (or introgression) of the trait(s) into inbred sweet cornline R660K is for example achieved by recurrent selection breeding, forexample by backcrossing. In this case, inbred sweet corn line R660K (therecurrent parent) is first crossed to a donor inbred (the non-recurrentparent) that carries the appropriate gene(s) for the trait(s) inquestion. The progeny of this cross is then mated back to the recurrentparent followed by selection in the resultant progeny for the desiredtrait(s) to be transferred from the non-recurrent parent. After three,preferably four, more preferably five or more generations of backcrosseswith the recurrent parent with selection for the desired trait(s), theprogeny will be heterozygous for loci controlling the trait(s) beingtransferred, but will be like the recurrent parent for most or almostall other genes (see, for example, Poehlman & Sleper (1995) BreedingField Crops, 4th Ed., 172-175; Fehr (1987) Principles of CultivarDevelopment, Vol. 1: Theory and Technique, 360-376).

The laboratory-based techniques described above, in particular RFLP andSSR, are routinely used in such backcrosses to identify the progenieshaving the highest degree of genetic identity with the recurrent parent.This permits to accelerate the production of inbred maize lines havingat least 90%, preferably at least 95%, more preferably at least 99%genetic identity with the recurrent parent, yet more preferablygenetically identical to the recurrent parent, except for the trait(s)introgressed from the donor patent. Such determination of geneticidentity is based on molecular markers used in the laboratory-basedtechniques described above. Such molecular markers are for example thosedescribed in Boppenmaier, et al., “Comparisons among strains of inbredsfor RFLPs”, Maize Genetics Cooperative Newsletter (1991) 65, pg. 90, orthose available from the University of Missouri database and theBrookhaven laboratory database. The last backcross generation is thenselfed to give pure breeding progeny for the gene(s) being transferred.The resulting plants have essentially all of the morphological andphysiological characteristics of inbred sweet corn line R660K, inaddition to the single gene trait(s) transferred to the inbred. Theexact backcrossing protocol will depend on the trait being altered todetermine an appropriate testing protocol. Although backcrossing methodsare simplified when the trait being transferred is a dominant allele, arecessive allele may also be transferred. In this instance it may benecessary to introduce a test of the progeny to determine if the desiredtrait has been successfully transferred.

Many traits have been identified that are not regularly selected for inthe development of a new inbred but that can be improved by backcrossingtechniques. Examples of traits transferred to inbred sweet corn lineR660K include, but are not limited to, waxy starch, herbicide tolerance,resistance for bacterial, fungal, or viral disease, insect resistance,enhanced nutritional quality, improved performance in an industrialprocess, quality and processing traits such as high processing plantrecovery, tender kernels, pleasing taste, uniform kernel size and color,attractive husk package and husked ears, ability to ship long distances,ease of mechanical or manual harvest, tipfill, row straight, alteredreproductive capability, such as male sterility or male fertility, yieldstability and yield enhancement. Other traits transferred to inbredsweet corn line R660K are for the production of commercially valuableenzymes or metabolites in plants of inbred sweet corn line R660K. Othertraits transferred to inbred sweet corn line R660K are also differentendosperm mutations including a sugary trait (su, e.g., su1), a shrunkentrait (sh, e.g., sh2), a brittle trait (bt, e.g., bt1 or bt2, not to beconfused with the gene for an endoxin from Bacillus thuringiensis,described elsewhere herein), or both white or yellow endosperm color.

Traits transferred to sweet corn inbred line R660K are naturallyoccurring maize traits, such as naturally occurring sweet corn traits,or are transgenic. Transgenes are originally introduced into a donor,non-recurrent parent using genetic engineering and transformationtechniques well known in the art. A transgene introgressed into sweetcorn inbred line R660K typically comprises a nucleotide sequence whoseexpression is responsible or contributes to the trait under the controlof a promoter appropriate for the expression of the nucleotide sequenceat the desired time in the desired tissue or part of the plant.Constitutive or inducible promoters are used. The transgene may alsocomprise other regulatory elements such as for example translationenhancers or termination signals. In one embodiment, the nucleotidesequence is the coding sequence of a gene and is transcribed andtranslated into a protein. In another embodiment, the nucleotidesequence encodes an antisense RNA or a sense RNA that is not translatedor only partially translated.

Where more than one trait is introgressed into inbred sweet corn lineR660K, it is preferred that the specific genes are all located at thesame genomic locus in the donor, non-recurrent parent, preferably, inthe case of transgenes, as part of a single DNA construct integratedinto the donor's genome. Alternatively, if the genes are located atdifferent genomic loci in the donor, non-recurrent parent, backcrossingallows to recover all of the morphological and physiologicalcharacteristics of inbred sweet corn line R660K in addition to themultiple genes in the resulting sweet corn inbred line.

The genes responsible for a specific, single gene trait are generallyinherited through the nucleus. Known exceptions are, e.g. the genes formale sterility, some of which are inherited cytoplasmically, but stillact as single gene traits. In one embodiment, a transgene to beintrogressed into sweet corn inbred line R660K is integrated into thenuclear genome of the donor, non-recurrent parent. In anotherembodiment, a transgene to be introgressed into sweet corn inbred lineR660K is integrated into the plastid genome of the donor, non-recurrentparent. In one embodiment, a plastid transgene comprises one genetranscribed from a single promoter or two or more genes transcribed froma single promoter.

In one embodiment, a transgene whose expression results or contributesto a desired trait to be transferred to sweet corn inbred line R660Kcomprises a virus resistance trait such as, for example, a MDMV strain Bcoat protein gene whose expression confers resistance to mixedinfections of maize dwarf mosaic virus and maize chlorotic mottle virusin transgenic maize plants (Murry et al. Biotechnology (1993) 11:155964). In another embodiment, a transgene comprises a gene encoding aninsecticidal protein, such as, for example, a crystal protein ofBacillus thuringiensis or a vegetative insecticidal protein fromBacillus cereus, such as VIP3 (see for example Estruch et al. NatBiotechnol (1997) 15:137-41). In one embodiment, an insecticidal geneintroduced into inbred sweet corn line R660K is a Cry1Ab gene or aportion thereof, for example introgressed into sweet corn inbred lineR660K from a maize line comprising a Bt-11 event as described in U.S.application Ser. No. 09/042,426 now U.S. Pat. No. 6,114,608,incorporated herein by reference, or from a maize line comprising a 176event as described in Koziel et al. (1993) Biotechnology 11: 194-200. Inyet another embodiment, a transgene introgressed into sweet corn inbredline R660K comprises an herbicide tolerance gene. For example,expression of an altered acetohydroxyacid synthase (AHAS) enzyme confersupon plants tolerance to various imidazolinone or sulfonamide herbicides(U.S. Pat. No. 4,761,373, incorporated herein by reference). In anotherembodiment, a non-transgenic trait conferring tolerance toimidazolinones is introgressed into sweet corn inbred line R660K (e.g.an “IT” or “IR” trait). U.S. Pat. No. 4,975,374, incorporated herein byreference, relates to plant cells and plants containing a gene encodinga mutant glutamine synthetase (GS) resistant to inhibition by herbicidesthat are known to inhibit GS, e.g. phosphinothricin and methioninesulfoximine. Also, expression of a Streptomyces bar gene encoding aphosphinothricin acetyl transferase in maize plants results in toleranceto the herbicide phosphinothricin or glufosinate (U.S. Pat. No.5,489,520, incorporated herein by reference). U.S. Pat. No. 5,013,659,incorporated herein by reference, is directed to plants that express amutant acetolactate synthase (ALS) that renders the plants resistant toinhibition by sulfonylurea herbicides. U.S. Pat. No. 5,162,602,incorporated herein by reference, discloses plants tolerant toinhibition by cyclohexanedione and aryloxyphenoxypropanoic acidherbicides, such as e.g. Sethoxydim or any herbicidally effective formsof2-[1-ethoxyimino)butyl]-5-(2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one,its salts and derivatives. The tolerance is conferred by an alteredacetyl coenzyme A carboxylase (ACCase). U.S. Pat. No. 5,554,798,incorporated herein by reference, discloses transgenic glyphosatetolerant maize plants, which tolerance is conferred by an altered5-enolpyruvyl-3-phosphoshikimate (EPSP) synthase gene. Also, toleranceto a protoporphyrinogen oxidase inhibitor is achieved by expression of atolerant protoporphyrinogen oxidase enzyme in plants (U.S. Pat. No.5,767,373, incorporated herein by reference).

In one embodiment, a transgene introgressed into sweet corn inbred lineR660K comprises a gene conferring tolerance to a herbicide and at leastanother nucleotide sequence encoding another trait, such as for example,an insecticidal protein. Such combination of single gene traits is forexample a Cry1Ab gene and a bar gene.

Specific transgenic events introgressed into sweet corn inbred lineR660K can be obtained through the list of Petitions of NonregulatedStatus granted by the United States Department of Agriculture set forthin the APHIS database. These are for example introgressed fromglyphosate tolerant event GA21 (9709901p), glyphosatetolerant/Lepidopteran insect resistant event MON 802 (9631701p),Lepidopteran insect resistant event DBT418 (9629101p), male sterileevent MS3 (9522801p), Lepidopteran insect resistant event Bt11(9519501p), phosphinothricin tolerant event B16 (9514501p), Lepidopteraninsect resistant event MON 80100 (9509301p), phosphinothricin tolerantevents T14, T25 (9435701p), Lepidopteran insect resistant event 176(9431901p).

The introgression of a Bt11 event into a maize line, such as sweet corninbred line R660K, by backcrossing is exemplified in U.S. applicationSer. No. 09/042,426 now U.S. Pat. No. 6,114,608, incorporated herein byreference, and the present invention is directed to methods ofintrogressing a Bt11 event into sweet corn inbred line R660K using forexample the markers described in U.S. application Ser. No. 09/042,426now U.S. Pat. No. 6,114,608 and to resulting maize lines.

Direct selection may be applied where the trait acts as a dominanttrait. An example of a dominant trait is herbicide tolerance. For thisselection process, the progeny of the initial cross are sprayed with theherbicide prior to the backcrossing. The spraying eliminates any plantwhich do not have the desired herbicide tolerance characteristic, andonly those plants which have the herbicide tolerance gene are used inthe subsequent backcross. This process is then repeated for theadditional backcross generations.

This invention also is directed to methods for producing a maize plant,preferably a sweet corn plant, by crossing a first parent maize plantwith a second parent maize plant wherein either the first or secondparent maize plant is a sweet corn plant of inbred line R660K or a sweetcorn plant of inbred line R660K further comprising one or more singlegene traits. Further, both first and second parent maize plants can comefrom the inbred sweet corn line R660K or an inbred sweet corn plant ofR660K further comprising one or more single gene traits. Thus, any suchmethods using the inbred sweet corn line R660K or an inbred sweet cornplant of R660K further comprising one or more single gene traits arepart of this invention: selfing, backcrosses, hybrid production, crossesto populations, and the like. All plants produced using inbred sweetcorn line R660K or inbred sweet corn plants of R660K further comprisingone or more single gene traits as a parent are within the scope of thisinvention. Advantageously, inbred sweet corn line R660K or inbred sweetcorn plants of R660K further comprising one or more single gene traitsare used in crosses with other, different, maize inbreds to producefirst generation (F1) maize hybrid seeds and plants with superiorcharacteristics.

In one embodiment, seeds of inbred sweet corn line R660K or seeds ofinbred sweet corn plants of R660K further comprising one or more singlegene traits are provided as an essentially homogeneous population ofinbred corn seeds. Essentially homogeneous populations of inbred seedare those that consist essentially of the particular inbred seed, andare generally purified free from substantial numbers of other seed, sothat the inbred seed forms between about 90% and about 100% of the totalseed, and preferably, between about 95% and about 100% of the totalseed. Most preferably, an essentially homogeneous population of inbredcorn seed will contain between about 98.5%, 99%, 99.5% and about 100% ofinbred seed, as measured by seed grow outs. The population of inbredcorn seeds of the invention is further particularly defined as beingessentially free from hybrid seed. Thus, one particular embodiment ofthis invention is isolated inbred seed of inbred sweet corn plants ofR660K, e.g. substantially free from hybrid seed or seed of other inbredseed, e.g., a seed lot or unit of inbred seed which is at least 95%homogeneous. The inbred seed population may be separately grown toprovide an essentially homogeneous population of plants of inbred sweetcorn line R660K or inbred sweet corn plants of R660K further comprisingone or more single gene traits.

Seeds of inbred sweet corn plants of R660K for planting purposes ispreferably containerized, e.g., placed in a bag or other container forease of handling and transport and is preferably coated, e.g., withprotective agents, e.g., safening or pesticidal agents, in particularantifungal agents and/or insecticidal agents.

When inbred sweet corn line R660K is identified herein, it is understoodthat the named line include varieties which have the same genotypic andphenotypic characteristics as the identified varieties, i.e., arederived from a common inbred source, even if differently named.

As used herein, the term “plant” includes plant cells, plantprotoplasts, plant cell tissue cultures from which maize plants can beregenerated, plant calli, plant clumps, and plant cells that are intactin plants or parts of plants, such as embryos, pollen, ovules, flowers,kernels, ears, cobs, leaves, husks, stalks, roots, root tips, anthers,silk, seeds and the like. Duncan, Williams, Zehr, and Widholm, Planta(1985) 165:322-332 reflects that 97% of the plants cultured thatproduced callus were capable of plant regeneration. Subsequentexperiments with both inbreds and hybrids produced 91% regenerablecallus that produced plants. In a further study in 1988, Songstad,Duncan & Widholm in Plant Cell Reports (1988), 7:262-265 reports severalmedia additions that enhance regenerability of callus of two inbredlines. Other published reports also indicated that “nontraditional”tissues are capable of producing somatic embryogenesis and plantregeneration. K. P. Rao, et al., Maize Genetics Cooperation Newsletter,60:64-65 (1986), refers to somatic embryogenesis from glume calluscultures and B. V. Conger, et al., Plant Cell Reports, 6:345-347 (1987)indicates somatic embryogenesis from the tissue cultures of maize leafsegments. Thus, it is clear from the literature that the state of theart is such that these methods of obtaining plants are, and were,“conventional” in the sense that they are routinely used and have a veryhigh rate of success.

Maize tissue culture procedures are also described in Green and Rhodes,“Plant Regeneration in Tissue Culture of Maize,” Maize for BiologicalResearch (Plant Molecular Biology Association, Charlottesville, Va.1982, at 367-372) and in Duncan, et al., “The Production of CallusCapable of Plant Regeneration from Immature Embryos of Numerous Zea maysGenotypes,” 165 Planta 322-332 (1985). Thus, another aspect of thisinvention is to provide cells which upon growth and differentiationproduce maize plants having the physiological and morphologicalcharacteristics of inbred sweet corn line R660K. In one embodiment,cells of inbred sweet corn line R660K are transformed genetically, forexample with one or more genes described above, for example by using atransformation method described in U.S. application Ser. No. 09/042,426now U.S. Pat. No. 6,114,608, incorporated herein by reference, andtransgenic plants of inbred sweet corn line R660K are obtained and usedfor the production of hybrid maize plants. Maize is used as human food,livestock feed, and as raw material in industry. Sweet corn is usuallyused as fresh produce, canning or freezing, for human consumption. Thefood uses of maize, in addition to human consumption of maize kernels,also include both products of dry- and wet-milling industries. Theprincipal products of maize dry milling are grits, meal and flour. Themaize wet-milling industry can provide maize starch, maize syrups, anddextrose for food use. Maize oil is recovered from maize germ, which isa by-product of both dry- and wet-milling industries.

Maize, including both grain and non-grain portions of the plant, is alsoused extensively as livestock feed, primarily for beef cattle, dairycattle, hogs, and poultry. Industrial uses of maize include productionof ethanol, maize starch in the wet-milling industry and maize flour inthe dry-milling industry. The industrial applications of maize starchand flour are based on functional properties, such as viscosity, filmformation, adhesive properties, and ability to suspend particles. Themaize starch and flour have application in the paper and textileindustries. Other industrial uses include applications in adhesives,building materials, foundry binders, laundry starches, explosives,oil-well muds, and other mining applications. Plant parts other than thegrain of maize are also used in industry: for example, stalks and husksare made into paper and wallboard and cobs are used for fuel and to makecharcoal.

The seed of inbred sweet corn line R660K or of inbred sweet corn lineR660K further comprising one or more single gene traits, the plantproduced from the inbred seed, the hybrid maize plant produced from thecrossing of the inbred, hybrid seed, and various parts of the hybridmaize plant can be utilized for human food, livestock feed, and as a rawmaterial in industry.

The present invention therefore also discloses an agricultural productcomprising a plant of the present invention or derived from a plant ofthe present invention. The present invention also discloses anindustrial product comprising a plant of the present invention orderived from a plant of the present invention. The present inventionfurther discloses methods of producing an agricultural or industrialproduct comprising planting seeds of the present invention, growingplant from such seeds, harvesting the plants and processing them toobtain an agricultural or industrial product.

Deposit

Applicants have made a deposit of at least 2500 seeds of inbred sweetcorn line R660K with the American Type Culture Collection (ATCC),Manassas, Va., 20110-2209 U.S.A., ATCC Deposit No: PTA-8532. Thisdeposit of the inbred sweet corn line R660K will be maintained in theATCC depository, which is a public depository, for a period of 30 years,or 5 years after the most recent request, or for the effective life ofthe patent, whichever is longer, and will be replaced if it becomesnonviable during that period. Additionally, Applicants have satisfiedall the requirements of 37 C.F.R. §§1.801-1.809, including providing anindication of the viability of the sample. Applicants impose norestrictions on the availability of the deposited material from theATCC; however, Applicants have no authority to waive any restrictionsimposed by law on the transfer of biological material or itstransportation in commerce. Applicants do not waive any infringement ofits rights granted under this patent or under the Plant VarietyProtection Act (7 USC 2321 et seq.).

The foregoing invention has been described in detail by way ofillustration and example for purposes of clarity and understanding.However, it will be obvious that certain changes and modifications suchas single gene modifications and mutations, somaclonal variants, variantindividuals selected from large populations of the plants of the instantinbred and the like may be practiced within the scope of the invention,as limited only by the scope of the appended claims.

1. Seed of inbred sweet corn line R660K, representative seeds of saidinbred sweet corn line having been deposited under ATCC Accession No:PTA-8532.
 2. A maize plant, or parts thereof, produced by growing theseed of claim
 1. 3. Pollen of the plant of claim
 2. 4. An ovule of theplant of claim
 2. 5. An ear of the plant of claim
 2. 6. A maize plant,or parts thereof, having all the physiological and morphologicalcharacteristics of a plant according to claim
 2. 7. A male sterile maizeplant, or parts thereof, otherwise having all the physiological andmorphological characteristics of a plant according to claim
 2. 8. Amaize plant according to claim 2, further comprising a single genetransferred trait which confers upon said maize plant tolerance to anherbicide.
 9. A maize plant according to claim 2, further comprising asingle gene transferred trait which is conferred by a transgene.
 10. Amaize plant according to claim 9, wherein said transgene comprises agene conferring upon said maize plant tolerance to an herbicide.
 11. Amaize plant according to claim 10, wherein said herbicide is glyphosate,gluphosinate, a sulfonylurea or an imidazolinone herbicide, ahydroxyphenylpyruvate dioxygenase inhibitor or a protoporphyrinogenoxidase inhibitor.
 12. A maize plant according to claim 9, wherein saidtransgene comprises a gene conferring upon said maize plant insectresistance, disease resistance or virus resistance.
 13. A maize plantaccording to claim 12, wherein said gene conferring upon said maizeplant insect resistance is a Bacillus thuringiensis Cry1Ab gene.
 14. Amaize plant according to claim 13, further comprising a bar gene.
 15. Atissue culture of regenerable cells of a maize plant according to claim2, wherein the tissue regenerates plants with all the morphological andphysiological characteristics of plants according to claim
 2. 16. Atissue culture according to claim 15, the regenerable cells beingselected from the group consisting of embryos, meristems, pollen,leaves, anthers, roots, root tips, silk, flowers, kernels, ears, cobs,husks and stalks, or being protoplasts or callus derived therefrom. 17.A method for producing maize seed comprising crossing a first parentmaize plant with a second parent maize plant and harvesting theresultant first generation maize seed, wherein said first or secondparent maize plant is the maize plant of claim
 2. 18. A method accordingto claim 17, wherein said first parent maize plant is different fromsaid second parent maize plant, wherein said resultant seed is a firstgeneration (F1) hybrid maize seed.
 19. A method for producing maize seedcomprising crossing a first parent maize plant with a second parentmaize plant and harvesting the resultant first generation maize seed,wherein said first or second parent maize plant is the inbred maizeplant of claim
 6. 20. A method according to claim 19, wherein said firstparent maize plant is different from said second parent maize plant,wherein said resultant seed is a first generation (F1) hybrid maizeseed.
 21. A method for obtaining a maize inbred line comprising: (a)planting a collection of seed comprising seed of a hybrid, one of whoseparents is either a plant according to claim 2 or a maize plant havingall the physiological and morphological characteristics of a plantaccording to claim 2, said collection also comprising seed of saidinbred line; (b) growing plants from said collection of seed; (c)identifying said inbred plants; (d) selecting said inbred plant; and e)controlling pollination in a manner which preserves the homozygosity ofsaid inbred plant.
 22. A method comprising introgressing one or moresingle gene traits into inbred sweet corn line R660K, seed of said linehaving been deposited under ATCC Accession No: PTA-8532, using one ormore markers for marker assisted selection among maize lines to be usedin a maize breeding program comprising at least four rounds ofbackcrossing into inbred sweet corn line R660K, the markers beingassociated with said one or more single gene traits, wherein theresulting maize line has essentially all the physiological andmorphological characteristics of a plant of inbred sweet corn line R660Kand further comprises said one or more single gene transferred traits.23. A method of producing a sweet corn ear comprising growing a plantaccording to claim 2 to produce an ear, and harvesting said ear.
 24. Amethod according to claim 23, further comprising isolating a kernel fromsaid ear.
 25. A method according to claim 24, further comprisingprocessing said kernel to obtain a sweet corn product.
 26. A methodaccording to claim 25, wherein said sweet corn product is a canned or afrozen product, or a fresh produce.
 27. A method of producing a sweetcorn product comprising obtaining an ear of a plant according to claim2, isolating a kernel from said ear, and processing said kernel toobtain a sweet corn product.
 28. A method according to claim 27, whereinsaid sweet corn product is a canned or a frozen product, or a freshproduce.